Parosteal Osteosarcoma
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![Bone_Osteosarcoma36_Parosteal.jpg](/slides-13/slides/Bone_Osteosarcoma36_Parosteal.jpg)
Comments:
Higher magnification showing hypocellular spindle stroma separating the bony trabeculae. The stromal spindle cells lack cytologic atypia or increased mitotic activity. The vast majority of parosteal osteosarcoma are Grade I tumors; approximately 20% have sufficient atypia to be classified as Grade II.